At last, a question for a literature student!
"When I was One and Twenty" is Housman, Dave. One of my personal favorites...I'd love to hear your arrangement of it!
W.B. Yeats wrote one of my all-time favorite poems: "Sailing to Byzantium". Absolutely gorgeous language...as my poetry professor put it, it makes you want to go in a corner and scream. His "Crazy Jane" poems are very cool stuff, though a little less musical. Another one of my favorite Yeats poems which would probably make a good song is "Easter 1916". Sad, but beautiful.
Now, what do I know about Yeats himself? Hold on while I get out my notes from Lit 214.
An Irishman born and bred, but a bit of an art school snob type. He had a long-standing fascination with one Maude Gonne, a fiery red-haired 6 foot tall beautiful Irish woman. She wouldn't have anything to do with him as anything more than a bit of fun, though, because he was "just a poet", not "a man of action". He writes some great poetry about her, though--some angry, some passionate, some wistful...so maybe it's best that he never got what he wanted, at least for those of us who like reading his poetry. :)